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How should we treat virtual methods exposed in APIs (Part 2)

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In postul precedent am descutat despre o problema care poate sa apara cand expunem intr-un API metode virtuale, care sunt apoi suprascrise de catre un alt dezvoltator. Iar o versiune ulterioara a API schimba comportamentul aplicatiei in asa fel incat suntem obligati sa schimbam codul care foloseste API expus.
Mai jos gasiti o posibila solutie la aceasta problema.
public abstract class FooBase
{
    private void DoAction()
     {
          // Custom code that can be executed by our method.           
          DoActionCore();           
          // More custom code that can be executed by our method.       
     }   

     public virtual void DoActionCore()   
     {              
          // Some action
     }
}

public class MyCustomFoo : FooBase
{   
     public override void DoActionCore()   
     {       
          // My custom code of MyCustomFoo that will be       
          // executed by DoAction method from base class.   
     }
}
O solutie de acest gen o sa functioneze, doar daca cel care expune API o sa o foloseasca de la prima versiune.
O alta varianta este ca metode DoActionCore sa fie declarata ca si abstracta, in cazul in care vrem sa obligam dezvoltatorul sa defineasca un comportament custom.
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Comments

  1. AnonymousJune 25, 2012 at 9:58 AM

    Solutia asta are si un nume - template method pattern (http://en.wikipedia.org/wiki/Template_method_pattern).

    E ok ca si metoda de a permite customizarea behaviour-ului unei clase cat timp nu apar ierarhii de clase pe mai mult de 2 nivele, si cat timp nu apare necesitatea ca pentru o singura metoda din clasa de baza sa se ofere mai multe puncte de extensie - in ambele cazuri template method (foarte folosit cu ceva ani in urma) duce la cod greu de inteles si de intretinut.

    ReplyDelete
    Replies
    1. Andrei RineaJune 25, 2012 at 11:26 AM

      Mersi Tudor ca acum pot sa pun titlu la un sablon pe care il cunosteam si foloseam ;)

      Delete
    2. AnonymousJune 25, 2012 at 1:17 PM

      :) e doar o conventie - si eu il foloseam cu 10 ani in urma si nu stiam cum l-au botezat..

      Delete

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